Advanced Audio Coding (AAC) has been proposed as the successor to the MPEG-1/2 Layer-3 format (commonly referred to as “MP3”) for high quality multi-channel audio transmission. AAC was first specified in the standard MPEG-2 Part 7, and later updated in MPEG-4 Part 3. AAC has found applications in digital audio broadcasting and storage applications such as in portable digital audio devices, the Internet and wireless communications.
Generally, for the AAC standard, the decoding algorithms are predetermined and fixed. However, there may be opportunities to manipulate the encoding algorithm while maintaining full decoder compatibility.
Some differences between AAC and MP3 include the AAC standard providing for the selection of quantization step sizes (which are differentially coded), and selection of Huffman codebooks from a set of 12 Huffman codebooks. Some conventional encoding algorithms are limited to optimization of these two parameters for optimization of rate-distortion in AAC encoding. These two parameters may thereafter be used to configure an encoder.
Similar reference numerals may have been used in different figures to denote similar components.